Credits · posting currency
Credits are the site's posting currency, not real money. Voting, commenting, and proposing solutions are all free. Posting a new problem spends one Credit, a small cost that keeps the front page free of drive-by noise, without ever charging you real money.
Credits are spent on the attempt, not the outcome. That's what makes them a real cost against spam rather than a paywall. One Credit is deducted the moment you publish a problem, whether or not it ends up going anywhere. Run out, and you can still vote, comment and propose solutions on everything already posted, you just can't start a new problem until you earn one back.
New accounts start with 10 Credits
Enough to try the site without earning anything first.
A problem you posted reaches 10 validations
Proof it was worth posting earns 1 Credit back, automatically, the moment it crosses the threshold.
A moderator removes one of your problems
The Credit is refunded, a post that never survived review shouldn't permanently cost you the attempt.
Credits cap at 25, there's no benefit to hoarding them beyond that.